The present invention pertains generally to sawmill carriages which serve to carry a log into saw engagement with the log being laterally positioned in increments by knees on the carriage.
Currently utilized on sawmill carriages are hydraulic cylinders which serve to position log positioning knees for successive cuts of the log. Such cylinders may be of the type providing a feedback signal to a programmable controller indicating the degree of cylinder piston rod extension to enable precise knee and log positioning. It is highly advantageous to adapt such state-of-the art hydraulic cylinders, commonly termed linear actuators, to existing log carriages however such is often complicated by the obstacle of restricted space as earlier sawmill carriages utilized other powered means such as chain drives for knee positioning. Accordingly, the refurbishing of some existing sawmill carriages with linear actuators of considerable length was not always possible or practical. Without the linear actuators and programmable controllers the competitive status of a sawmill is jeopardized. The physical altering of sawmill premises to provide the additional space is not economically feasible in many instances.
U.S. Pat. No. 4,344,609 discloses a sawmill carriage having a log positioning knee controlled by a hydraulic cylinder with a pneumatic cylinder disposed thereabout for the purpose of absorbing log imparted impact loads against the knee and hydraulic cylinder. U.S. Pat. No. 4,037,502 discloses a sawmill carriage with a log positioning knee controlled by axially aligned cylinders which are extended or retracted in a cumulative manner to provide large and small increments of log positioning. U.S. Pat. No. 1,804,716 discloses a sawmill carriage having knee assemblies each responsive to multiple cylinders with one cylinder being a taper setting cylinder which supplements a primary knee positioning cylinder for the purpose of providing for cutting of a piece of lumber inclined to the major axis of the log.